Millions of patients within the United States alone suffer from cutaneous syndromes, severe wounds, and skin tumors each year. Tissue replacement therapy using stem cells of the skin would provide for the clinical lack of understanding of the factors that function to maintain the stem cell population. P63 is a p53 homologue that is expressed within epidermal stem cells and is essential for the early stages of morphogenesis of the skin and its appendages. The goal of this project is to examine the functional role of p63 in the maintenance and/or differentiation of epidermal stem cells. P63 is essential for development; mice that lack p63 die shortly after birth, thereby preventing a detailed analysis of p63 function within stem cells of the adult skin. Therefore, a system for inducible ablation if p63 is needed to evaluate the function of p63 within the epidermal stem cell. LoxP/Cre technology will be used to generate a mouse model that can be used to isolate primary keratinocyte cultures that can be used to examine the effect of p63 loss on the maintenance and differentiation of epidermal stem cells. These cells will provide an in vitro model to isolate p63 target genes, and to assess the function of distinct p63 proteins. Four Specific Aims are proposed: 1. Functional evaluation of the floxed p63 allele in vivo. 2. Generation of primary keratinocytes from skin of p63 deficient and p63 conditional mouse models. 3. Functional analysis of p63 deficiency. 4. Rescue of the p63 deficient phenotype with distinct p63 isoforms. The proposed studies will generate a model that will be used to define the function of p63 within the epidermal stem cell. This work will provide the basis for the clinical treatment of numerous dermatological diseases and injuries.